Aviation stands at a structural crossroads. Retrofitting conventional tube-and-wing airframes with zero-emission liquid hydrogen (LH₂) powertrains introduces unacceptable penalties: low volumetric utility, excessive parasitic weight, and severe nacelle drag scaling.
This article presents the ultimate ground-up hydrogen aviation architecture: a Truncated Blended Wing Body (BWB) Box-Wing Biplane powered by an integrated H₂/LOX Fluidic Shear-Layer Ejector System. By replacing mechanical turbomachinery with static, high-aspect-ratio planar slit ejectors, and replacing passive airfoils with active top-surface Boundary Layer Ingestion (BLI), this design decouples lift generation from forward velocity while eliminating engine dry-mass and nacelle drag penalties.
1. Aerodynamic Topology: Truncated BWB + Box-Wing Biplane
Traditional BWB designs thin down at the outer wing edges to maintain an unbroken monoplane profile. This creates large wetted surface areas that yield low internal volume while generating high skin-friction drag.
Key Structural & Aerodynamic Features
Truncated Centerbody: The lower BWB centerbody is truncated laterally at the exact point where internal height drops below structural and tankage utility (<1.5 m). This retains 100% of the deep center section for conformal liquid hydrogen and oxygen storage.
Prandtl’s Best Wing System: Outboard lifting loads are handed off to a slender, high-aspect-ratio upper wing connected to the BWB centerbody via vertical box-frame endplates. This closed-loop wing system suppresses tip-vortex decay, reducing induced drag by 20–30% relative to a monoplane of equal span.
Dual-Function Endplate Stabilizers: The outboard vertical box endplates sit in clean, undisturbed airflow outside the centerbody wake, acting as primary vertical stabilizers with split drag-rudders (decelerons). This eliminates central vertical tail structures and provides directional control authority during steep nose-up hover transitions.
2. Propulsion Architecture: Pure Fluidic H₂/LOX Shear-Layer Ejector
The propulsion system eliminates mechanical fan blades, turbine discs, rotating shafts, and dynamic seals, operating as a Zero-Moving-Part Fluidic Ejector Engine.
Thermochemical and Fluidic Mechanics
1. Fuel-Rich Gas Generator (2:1 Mass Ratio): Operating the primary combustor at a 2:1 LOX:LH₂ mass ratio keeps combustion temperatures low (≈ 1000-1300 K) due to the massive thermal capacity of unburned gaseous hydrogen. This low-pressure, low-temperature regime allows the combustor and nozzle manifold to be fabricated in flat, structural airframe shapes without complex cooling jackets.
2. High-Aspect-Ratio Planar Slit Nozzles: The primary gas generator exhaust expands through thin, linear slit nozzles. Unlike circular nozzles, planar slits provide an extreme surface-area-to-volume ratio, allowing viscous shear stress to instantly penetrate the jet boundary. Momentum transfer to entrained air occurs across a short channel length, eliminating internal vortex generators or heavy mixing cavities.
3. Spontaneous Ducted Auto-Ignition (Afterburning): As the entrained atmospheric air mixes into the channel, its 21% O₂ content meets the superheated, fuel-rich GH₂ exhaust (>850 K). Hydrogen auto-ignites instantly, causing volumetric gas expansion directly inside the unconfined ducted channel and accelerating the flow prior to reaching the trailing-edge nozzle.
3. Active Aerodynamics: Drag-Free High-Bypass Ratio & Blown Lift
Conventional high-bypass turbofans trade larger fan diameters for propulsive efficiency, incurring heavy penalties in nacelle frontal area, skin friction, and transonic wave drag.
The Lift and Altitude Multipliers
Active Boundary Layer Ingestion: By placing suction slots along the top of the BWB centerbody, the ejector system continuously ingests low-momentum boundary layer air. This suppresses boundary layer thickness, prevents flow separation, and maintains low skin friction drag.
Active Upper-Surface Vacuum: Entraining air vertically through upper slots forcibly drops the static pressure across the BWB centerbody. Every kilogram of bypass air pulled into the engine actively generates aerodynamic lift (L = (Pbottom - Ptop) • S), decoupling lift generation from aircraft forward velocity.
Trailing-Edge Super-Circulation (Coanda Effect): Exhausting the afterburned, high-velocity jet sheet directly over the trailing-edge control surfaces creates a fluidic flap. This prevents high-pressure under-wing air from leaking over the trailing edge, artificially extending the aerodynamic chord length and boosting the effective Lift-to-Drag ratio (L/D > 25).
High-Altitude Cruise Optimization: Because the core H₂/LOX gas generator carries its own oxidizer, turbine power and ejector suction do not choke in thin upper-atmosphere air. Operating at cruising altitudes above 15,000 m cuts ambient atmospheric density in half, driving down airframe friction drag while maintaining active lift.
4. Internal Architecture, Safety, and Pitch-Up VTOL
Moving to a wide-body BWB layout solves the key internal volume, acoustic, and thermal constraints associated with high-power cryogenic aircraft.
Internal Safety and Layout Advantages
1. Lateral Propellant Shielding: Passengers reside within a central, structural pressure vessel. Cryptographic LH₂ and dense LOX conformal tanks are positioned in the outer blended flanks of the BWB centerbody, serving as lateral crash buffers while isolating cryogenic temperature gradients from passenger floors.
2. Acoustic Decoupling: Fluidic suction slots and ejector mixing channels are mounted laterally along the outer blended wing roots. This isolates the acoustic energy generated by shear-layer mixing from the passenger compartment.
3. Nose-Bottom Pitch-Up Rocket VTOL: The aircraft utilizes a dedicated nose-bottom rocket engine to kick the nose up into a vertical pitch angle (45°-90°) for takeoff and landing. The wide BWB keel absorbs the concentrated pitching thrust, while the outboard position of the air-suction slots prevents hot rocket exhaust from being re-ingested into the ejector channels during hover.
5. Architectural Performance Summary
Conclusion
By unifying the structural volume of a Blended Wing Body, the induced-drag efficiency of a Prandtl box-wing biplane, and the mechanical simplicity of an H₂/LOX fluidic ejector, this architecture redefines hydrogen flight. The aircraft trades heavy, static turbine mass for consumable LOX, rapidly lightening during climb to maximize cruise efficiency, while using active top-surface suction to convert engine bypass air directly into aerodynamic lift.
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